Dufay's body of isorhythmic motets may be the single most imposing aspect of his musical output. Although that is a bold statement, given the relative lack of attention they continue to receive, their relative stature in the genre is simply unparalleled. If Dufay's songs often melt seamlessly into the styles of those of the surrounding generations, and are matched in sophistication by his contemporary Binchois, Dufay's isorhythmic motets stand out instead as a unique summit of the genre. Likewise, if Dufay's masses and hymns follow English precedents, the structural sophistication of his isorhythmic motets can be approached only by perhaps a handful of English works (and even those by apparent Frenchmen such as Pycard). Moreover, nearly every isorhythmic motet is traced to a specific historical circumstance of some significance, making these Dufay's most public & spectacular compositions.
As in the case of the songs, the motets continue to be relatively neglected, but are performed completely in a single collection. In this case, the frequent use of instruments makes the performance somewhat old-fashioned in its outlook, although it does exhibit a good attention to detail. The program includes Dufay's 13 authentic isorhythmic motets, one of disputed authorship, seven shorter isorhythmic motets by Machaut to serve as an orientation, and a modest selection of what are termed Dufay's "cantilena" motets. The latter are essentially the stylistic development of his early hymn technique, taken to a more sophisticated level and sharing much with the style of his later cantus firmus masses. Although the set is 3 CDs, including the other items, Dufay's complete isorhythmic motets would fit in just under 80 minutes for a single CD, even at the stately pace of the present collection. It is a wonder no one else has attempted such a single CD program. [Note 06/01/00: And now they have.] The surviving isorhythmic motets are confined chronologically to the period 1420-46, but use a wide variety of political, secular, and sacred lyrics. There is certainly speculation that some later examples have been lost or survive only anonymously.
The isorhythm, a repeated structural rhythmic pattern, was put to use immediately in the genre of the motet with its multiple texts. Isorhythm was the perfect technical vehicle by which to unify such disparate material in contrapuntal intricacy, and so the ascendance of the motet form circa 1300 may have been a primary motivation for the Ars Nova notation itself. The ambivalence of the motet's combined sacred-secular genesis in the thirteenth century also stayed with it into the era of Dufay, buoyed by the structural clarity of isorhythm from the early fourteenth century onward. Some of the earliest such applications tend to be harsh and unrelenting, but nonetheless present a stimulating intellectual organization. It was Machaut, with his Ars Antiqua nuances, who brought a lyricism back to the Ars Nova motet, and it was such a lyricism which clearly infused Dufay's works in the form as well. In their hands, the motet became both personally expressive as well as an intellectual tour-de-force, leading to its transformation into a primarily personal vehicle (now without multiple texts, the one-time raison d'être!) in the hands of Josquin et al.
Among Dufay's surviving isorhythmic motets, two are in five parts, one is in three parts, and the remainder are in four parts. There is no particular sense of progression from fewer to more voices in Dufay's oeuvre, especially as isorhythmic pieces for these numbers were well-known from the previous era. Those in three & four parts had been dominant, and so after the conventionally Machaut-styled Vasilissa ergo of 1420, Dufay already attempted extravagance with the five-part Apostolo glorioso, a piece which is yet to be especially assured. With O sancte Sebastiane, despite its obvious homage to the style of Machaut, Dufay is secure in an idiom which is distinctly personal. Its basic pliability, lyricism, and forward momentum mark this motet as one of uncommon technical command. The slightly earlier O gemma lux & Rite majorem, show important points toward this development, as they become more assured, and in the case of the latter both more fluid & technically demanding. By 1431, Balsamus et munda received its debut in a ceremony led by the Pope! At that point, Dufay's isorhythmic motets were comparable in their combination of intellectual & expressive power only to his own compositions in the form. In the contemporaneous Ecclesie militantis, he made much more impressive use of five-voice counterpoint, as well as began writing motets in more than two sections, in this case by a sort of compound 3:2:3 ratio. None of the following motets use the standard bipartite acceleration. In Supremum est mortalibus, Dufay used a non-isorhythmic coda after two isorhythmic sections, and then each of the later motets is in three or four isorhythmic sections linked by various proportions.
It becomes increasingly impractical to make fully appropriate remarks about each successive masterpiece, but mention must be made of Nuper rosarum flores as justifiably Dufay's most famous motet and of Moribus et genere as his last surviving work in the genre. Dufay's control of forward momentum increases dramatically in this period, as these works no longer merely accelerate masterfully, but ebb & flow in various proportions. To finish the survey, I will name Salve flos, Fulgens iubar, & Magnanime gentis as impressive works which also deserve attention; the former is the one motet with texts securely attributed to Dufay, while the latter is his one three-part isorhythmic motet. With the text setting and imitation of his final settings (Moribus et genere & Fulgens iubar), Dufay begins to project a more modern style for the isorhythmic motet. However, the genre ended essentially with him, as the lone later example of consequence is Compère's Omnium bonorum plena, an homage to Dufay only evoking the strict isorhythmic style. Dufay's late non-isorhythmic motets such as O proles Yspanie and Ave regina coelorum are more prescient, as neither Ockeghem nor Josquin even attempted the isorhythmic genre, but did clearly draw inspiration from Dufay's "cantilena" style.
The stylistic motivations for Dufay's extravagant isorhythmic settings are perhaps unclear, yet also the almost inevitable final flowering of the genre. Despite being only a second class poet himself, it is Dufay's response to grammatical structure and semantics which marks his work most clearly as continuing the style of Machaut, to the point that he almost had to have been familiar with Machaut's four-part motets in spite of the intervening seven decades. Dunstable's use of more than two sections in his isorhythmic motets may have inspired Dufay, yet the relatively simple textures & phrasing of Dunstable's motets are far removed from even Dufay's earliest work in the medium. Such motivations seem to enter Dufay's idiom only later, and then paradoxically only when he was writing isorhythmic structures of unprecedented complexity. The nuanced phrasing and complicated lexical structures again mark Dufay's idiom as characteristically French, yet much of it was written in Italy. One encounters similar expatriate origins in the other possible precedents for the complexity of Dufay's work: A few of Ciconia's motets, the enigmatic mass movements of Pycard, and the "O"-antiphon cycle from Cyprus frequently show a detached pointillism, however, which is not characteristic of Dufay. [Note 09/25/01: I have neglected to discuss the connection between Dufay's work in this genre and the handful of pieces by such close compatriots as Loqueville (d.1418), Hugo de Lantins (fl.1420-30), and Johannes Brassart (c.1400-1455); the obscurity of their work today does not serve to demand such a comparison here, but this omission is an easy source of misunderstanding.] Again, it is Dufay's melodic grace which allows him to achieve such a summit of late medieval style.